Uniform Stream Research Articles

High-Dimensional Flow Cytometry Analysis of Regulatory Receptors on Human T Cells, NK Cells, and NKT Cells.

The field of flow cytometry has witnessed rapid technological advancements in the last few decades. While the founding principles of fluorescent detection on cells (or particles) within a uniform fluid stream remains largely unchanged, the availability more sensitive cytometers with the ability to multiplex more and more florescent signals has resulted in very complex high-order assays. This results in the co-use of fluorophores with increased levels of emission overlap and/or spillover spreading than in years past and thus requires careful and well thought out planning for flow cytometry assay development. As an example, we present the development of a large 18-color (20 parameter) flow cytometry assay designed to take an in depth analysis of effector lymphocyte phenotypes, with careful attention to assay controls and panel design.

On two-dimensional acoustic-entropy waves in a mean flow with uniform velocity and laterally varying sound speed

Acoustic-entropy waves are considered as linear, compressive perturbations of a non-dissipative non-homentropic uniform flow. The acoustic-entropy wave equation for the pressure satisfies a modified convected wave equation with non-uniform sound speed. In the case of plane flow with a linear entropy shear profile the exact solution is obtained in terms of Bessel functions of an exponential variable. The acoustic-entropy waves in a uniform flow with a linear entropy shear are considered in: (i) a parallel sided duct; (ii) an unbounded boundary over a flat wall; (iii) a boundary layer of finite thickness matched to a uniform free stream.

Mixed Convective Conditions on Natural Convection of MHD Blasius and Sakiadis Flows with Variable Properties and Nonlinear Chemical Reaction

An unsteady two-dimensional boundary layer slip flow of a viscous incompressible fluid moving plate in a quiescent fluid (Sakiadis flow) and the flow-induced over a stationary flat plate by a uniform free stream (Blasius flow) are investigated simultaneously, from a numerical point of view. The variable thermal conductivity, viscosity ratio parameter, and nonlinear chemical reaction are used in the governing equations. Similarity equations of the governing transport equations are converted into an ordinary differential equation. The transformed equations are solved numerically using the Runge-Kutta method via the shooting technique. Sample results for the dimensionless velocity, temperature, and concentration distributions are studied through graphically. Moreover, friction factor, heat, and mass transfer rates have been discussed in detail. The chemical reaction parameter decelerates the friction factor and heat transfer rates for the Sakiadis and Blasius flow cases and enhances in mass transfer rate in both cases. The rate of mass transfer is higher in Blasius flow compared with Sakiadis flow. The present results of the heat transfer rate are compared with the published results are found to be in good agreement.

New exotic capillary free-surface flows

Abstract

Tropical Cyclone in the North of the South China Sea as a Factor Affecting the Structure of the Vietnamese Current

Tropical cyclones play a significant role in the formation of the hydrodynamic regime of the South China Sea, including its western part, which is bordered by the coast of Vietnam. In this region, the main hydrodynamic structure is the Vietnamese (western boundary) Current. Its structure depends on both seasonal monsoons and tropical cyclones. Therefore, the study of this dependence is an important task for Vietnamese scientists. The results of these studies are not only of scientific, but also of great practical importance, because the social and economic development of Vietnam largely depends on the activity and variability of synoptic and hydrodynamic processes in this region. This paper presents the results of joint Russian–Vietnamese studies on the dependence of the vertical structure of the Vietnamese current on tropical Pacific cyclones in the north of the South China Sea during the interseasonal winter–summer period. This study is based on numerical modeling. The calculations were performed for April–June 1999, for which the necessary initial field data are available. The simulation results indicated that the Vietnamese Current during this time period is not a uniform stream of water masses. Instead, the structure of water masses in this region is governed by a strong anticyclonic circulation and a deep cyclonic circulation, which are responsible for the complex pattern of the Vietnamese Current. The Vietnamese Current transfers coastal water masses in the summer mode (from south to north) within the anticyclonic circulation and in the winter mode (from north to south) within the cyclonic circulation.

Flight Effects on Turbulent-Jet Wave Packets

An investigation is carried out to evaluate how an external uniform stream affects turbulent-jet coherent structures. The presence of this uniform stream outside the jet represents the effect of forward flight on the velocity field. Coherent structures are modelled as wave packets, and the flight effect is studied using the parabolized stability equations (PSEs). Measurements of mean base flows and axial velocity fluctuations on the jet centerline at assumed flight conditions are described. The velocity fields were supplied to a PSE model to retrieve the wave packet signatures of axial velocity fluctuations. Overall results are in good agreement with experimental measurements. There is an observed increase in wave packet wavelengths and phase velocities (with respect to the nozzle) as flight velocity increases. Also, axial amplification rates are determined and show stabilization in the near-nozzle region, which is confirmed by experimental power spectral densities on the jet centerline. This tendency holds as the freestream velocity increases.

Reach‐scale bankfull channel types can exist independently of catchment hydrology

AbstractReach‐scale morphological channel classifications are underpinned by the theory that each channel type is related to an assemblage of reach‐ and catchment‐scale hydrologic, topographic, and sediment supply drivers. However, the relative importance of each driver on reach morphology is unclear, as is the possibility that different driver assemblages yield the same reach morphology. Reach‐scale classifications have never needed to be predicated on hydrology, yet hydrology controls discharge and thus sediment transport capacity. The scientific question is: do two or more regions with quantifiable differences in hydrologic setting end up with different reach‐scale channel types, or do channel types transcend hydrologic setting because hydrologic setting is not a dominant control at the reach scale? This study answered this question by isolating hydrologic metrics as potential dominant controls of channel type. Three steps were applied in a large test basin with diverse hydrologic settings (Sacramento River, California) to: (1) create a reach‐scale channel classification based on local site surveys, (2) categorize sites by flood magnitude, dimensionless flood magnitude, and annual hydrologic regime type, and (3) statistically analyze two hydrogeomorphic linkages. Statistical tests assessed the spatial distribution of channel types and the dependence of channel type morphological attributes by hydrologic setting. Results yielded 10 channel types. Nearly all types existed across all hydrologic settings, which is perhaps a surprising development for hydrogeomorphology. Downstream hydraulic geometry relationships were statistically significant. In addition, cobble‐dominated uniform streams showed a consistent inverse relationship between slope and dimensionless flood magnitude, an indication of dynamic equilibrium between transport capacity and sediment supply. However, most morphological attributes showed no sorting by hydrologic setting. This study suggests that median hydraulic geometry relations persist across basins and within channel types, but hydrologic influence on geomorphic variability is likely due to local influences rather than catchment‐scale drivers. © 2020 John Wiley & Sons, Ltd.

Study on linear bio-structure print process based on alginate bio-ink in 3D bio-fabrication

Ink-jet printing is a non-impact printing technology in which drops jetted from an orifice onto a designated position. This technology can digitally transport fluids containing cells precisely onto desired substrates to construct three-dimensional organs. In order to obtain the stable uniform droplets, a stream is the key point of this technology. However, there are so many factors that affect the uniform droplet stream construction process: print parameters, material parameters, control method, etc. A good understanding of the various coupled transport processes that occur during bio-ink impact and spreading on bio-structure can improve the success of print-ability. This paper aims to obtain a good linear bio-structure with ink-jet printing technology. First, a typical droplet deposition process model is constructed; including droplet dynamics impact models and droplet diffusion cap models. Second, a model of successive droplet overlap, to form linear bio-structures, is constructed. Third, the finite element method is used to simulate the droplet impact, collision, and fusion process. Finally, the main influencing factors of the continuous injection printing process, namely the time interval between consecutive droplets and the droplet contact angles, are discussed. Sodium alginate is selected as bio-ink to verify the theory, and it is found that a good linear bio-structure could be obtained if the printing parameters are controlled optimally, i.e., if the initial contact angle is set as 60 degrees and the trigger frequency is set as 150 kHz. With a proper printing speed and gel coating, a good survival rate of printed cells could be obtained.

Effects of wave-field nonlinearity on motions of ship advancing in irregular waves using HOS method

The effects of incident-wave nonlinearity on motions of ships advancing in irregular waves are investigated here in statistical sense. The study is carried out by exploiting the combination of HOS method (High Order Spectral method) and time-domain Rankine source method incorporated with HOBEM (Higher-order Boundary Element Method). In the proposed model, HOS method is employed to simulate nonlinear irregular wave fields in cubic order and Rankine source method incorporated with HOBEM is applied to compute ship wave potential as well as disturbed potential, the equations of motions of ship advancing with constant forward speed in nonlinear waves are further established. Instead of employing simplified steady flow models such as uniform stream, steady ship wave potential is computed beforehand and applied to solve ship motions. Weakly nonlinear scheme considering nonlinear F–K (Froude-Krylov) and restoring forces is adopted.The proposed model is first validated in the case of linear regular and irregular waves via comparisons to experiment data and then applied to three different irregular sea states defined by spectrum with respective BFIs (Benjamin-Feir index). A series of long-time numerical simulations are carried out for both linear wave cases and nonlinear ones, and the statistical properties of nonlinear incident waves and the induced influence on ship motions are investigated and further analyzed. The analysis reveals that with large BFI, the skewness and kurtosis of wave surface elevation manifest departures from Gaussian values and the probability density function (p.d.f.) of the surface elevation performs departures from Gaussian behavior. In nonlinear cases, p.d.f. of instantaneous motions and motion amplitudes as well as exceedance probability of motion amplitudes are notably different from their linear counterparts. Higher possibilities for large motions occur in nonlinear cases.

Stagnation Flow and Heat Transfer From a Finite Disk Situated Perpendicular to a Uniform Stream

Abstract The stagnation flow and heat transfer from the blunt surface of a finite circular disk subjected to a uniform stream of an incompressible fluid is revisited in this paper. A laminar boundary layer analyses were carried out employing the method developed by Frössling. The involved auxiliary functions were calculated for several Prandtl numbers. It was found that the exact knowledge of the velocity at the outer edge of the boundary layer was essential to achieve an accurate velocity solution. In addition to the analytical work, computational fluid dynamics (CFD) simulations and a detailed experimental study were conducted including heat transfer measurements in a wind tunnel and a large water towing tank. The analytical treatment enabled a clear discussion of the effect of the Prandtl number on convective heat transfer from a blunt disk. A primary effect and a secondary effect were distinguished based on the analytical treatment. The boundary layer theory offered a rather efficient calculation method, and its results were in an excellent agreement with experimental data.

Dual solutions on boundary-layer flow over a moving surface in a flowing nanofluid with second-order slip

The steady boundary-layer flow of a nanofluid past a moving semi-infinite flat plate in a uniform free stream in the presence of second order slip is studied using a second order slip flow model. The governing PDE are transformed into non-linear ODE by using appropriate similarity transformations, which are then solved numerically using bvp4c solver for different values of selected parameters. We found that the solutions existed for dual in a certain range of velocity ratio parameter. Therefore, a stability analysis has been analyzed to show which solutions are stable. The effects of velocity ratio parameter, Lewis number, Prandtl number, Brownian motion parameter, thermopherosis parameter, mass suction, first order slip parameter, and second order slip parameter on the skin friction coefficient, heat transfer coefficient, dimensionless velocity, temperature as well as nanoparticle volume fraction profiles are figured out graphically and discussed. These results reveals that the slip parameters expand the range of the solutions obtained. The increment of slip parameters lead to decrease the skin friction coefficient while increase the heat transfer coefficient. In addition, the value of Lewis nmber, Prandtl number, Brownian motion parameter, and thermopherosis parameter are significantly affected the heat transfer coefficient. Lastly, the first solution is stable and physically relevant, while the second solution is not.

The Deformation and Stability of an Elastic Cell in a Uniform Flow

The deformation and stability of a two-dimensional inextensible elastic cell in an inviscid uniform stream are investigated using a conformal mapping method. At low flow speeds equilibrium solution...

Profiling Cell-Matrix Adhesion Using Digitalized Acoustic Streaming.

Profiling the kinetics of cell-matrix adhesion is of great importance to understand many physiological and pathological processes such as morphogenesis, tissue homeostasis, wound healing, and tumorigenesis. Here, we developed a novel digital acoustofluidic device for parallel profiling cell-matrix adhesion at single-cell level. By introduction of localized and uniform acoustic streaming into an open chamber microfluidic device, the adherent cells within the open chamber can be detached by the streaming-induced Stokes drag force. By digital regulation of pulsed acoustic power from a low level to high levels, the hundreds of adherent cells can be ruptured from the fibronectin-coated substrate accordingly, and their adhesive forces (from several pN to several nN) and kinetics can be determined by the applied power and cell incubation time. As a proof-of-concept application for studying cancer metastasis, we applied this technique to measure the adhesion strength and kinetics of human breast cancer cells to extracellular matrix such as fibronectin and compared their metastatic potentials by measuring the rupture force of cancer cells representing malignant (MCF-7 cells and MDA-MB-231 cells) and nonmalignant (MCF-10A cells) states. Our acoustofluidic device is simple, easy to operate, and capable of measuring, in parallel, hundreds of individual cells' adhesion forces with a resolution at the pN level. Thus, we expect this device could be widely used for both fundamental cell biology research as well as development of cancer diagnostics and tissue engineering technologies.

Heat transfer from a non-isothermal rotating rough disk subjected to forced flow

This communication aims to report heat transfer characteristics from a non-isothermal wavy disk rotating in a forced flow. The primary objective of this kind of studies is to seek a suitable mechanism for the quick removal of heat energy from a rotating disk surface. The achievement of an efficient mechanism which ensures a further higher rate of heat transfer is a fundamental goal in such studies. In this regard active and passive techniques are of fundamental importance whereby the current study utilizes a combination of both. There are three key elements, namely, the non-uniform disk temperature; surface roughness, and a radial free flow, which are responsible for the augmentation of the heat transfer. The analysis has been carried out for a variety of fluids depicting the increased rate of heat transfer due to a variation of these different elements. In doing so, the local and global heat transfer rates are manipulated in order to obtain a clear picture of the heat transfer process at a corrugated disk. The considered rough non-isothermal disk (with two sinusoids) rotating in the uniform stream of air (Pr = 0.71) leads to a significant (about 263%) enhancement in the overall heat transfer rate compared to that of a flat free rotating disk having surface temperature as quatratic function of the radial coordinate. Moreover, some threshold values (which correspond to seizing the heat transfer process) of the used power-index of the disk temperature (Tw − T∞ = c0rn∗) are also identified which are observed to vary slightly due to the surface irregularities and the relative motion of fluid and disk.

Film cooling performance measurement over a flat plate for a single row of holes embedded in an inclined trench

Film cooling heat transfer coefficient and effectiveness measurements downstream of a single row of holes embedded in an inclined trench injecting secondary fluid into the mainstream over a flat surface are reported here. The well-studied trench geometry is one where the walls of the trench are perpendicular and film injection holes are at an angle to the mainstream flow direction. In the current investigation, the trench is inclined at an angle to the mainstream and the injection holes are normal to the flow direction. Coolant injection in the form of a uniform stream at an angle to the mainstream is likely with this configuration. The trench inclination is kept constant at 35° and three hole pitch to diameter ratios equal to 3, 4.5 and 6 are studied for the blowing ratio varying between 0.3 and 2.5. The injection hole length to diameter ratios equal to 1.8 and 5.5 were studied and the influence on the net heat flux reduction ratio was found to be very small. The local effectiveness and the heat transfer coefficient values are presented and the variations in the cross-stream direction are observed to be very small. The effectiveness values for the current angular trench are higher whereas the heat transfer coefficients are smaller compared to the normal trench at higher blowing ratios. This results in increased Net Heat Flux Reduction ratio (NHFR) values for the current configuration which are observed to remain high at large downstream locations also.

Impact of Nonlinear Chemical Reaction and Melting Heat Transfer on an MHD Nanofluid Flow over a Thin Needle in Porous Media

A novel mathematical model is envisioned discussing the magnetohydrodynamics (MHD) steady incompressible nanofluid flow with uniform free stream velocity over a thin needle in a permeable media. The flow analysis is performed in attendance of melting heat transfer with nonlinear chemical reaction. The novel model is examined at the surface with the slip boundary condition. The compatible transformations are affianced to attain the dimensionless equations system. Illustrations depicting the impact of distinct parameters versus all involved profiles are supported by requisite deliberations. It is perceived that the melting heat parameter has a declining effect on temperature profile while radial velocity enhances due to melting.

Inviscid flow analysis of a circular cylinder traversing across an unbounded uniform-shear stream

The present study is focused on obtaining the inviscid flow solution for a circular cylinder traversing steadily across an unbounded uniform-shear flow. The work is motivated by understanding the aerodynamics of bodies traversing across a shear flow, as well as by developing an understanding of fundamental concepts that are well understood for uniform free stream but not in the presence of shear. The results show that, in general, the presence of shear makes it impossible to define a unique approach-stream incidence angle relative to the cylinder. However, in the limit of, what we have termed ‘quasi-uniform’ flow, such an angle can be defined. We show that in this limit, the flow is also quasi-steady, and the static-cylinder solution can be used to solve for the moving-cylinder problem with good accuracy. This ‘quasi-uniform and quasi-steady’ (QUS) condition is attained when a single unsteadiness parameter approaches zero. For small values of the cylinder-to-free-stream velocity ratio , , where is the effective non-dimensional shear rate. Away from the QUS flow limit, the flow field and the surface pressure distribution are significantly different between the moving and the static cylinders. However, a surprising result is that regardless of whether QUS conditions hold, the force acting on the moving cylinder in a Galilean frame of reference is always the same as that on a static cylinder in uniform-shear free stream but with non-dimensional shear rate and incidence angle equal to the moving cylinder’s instantaneous and , respectively.

Vortex-induced vibration and galloping of a circular cylinder in presence of cross-flow thermal buoyancy

The effect of cross-flow thermal buoyancy on vortex-induced vibration (VIV) of a circular cylinder is numerically investigated. An in-house fluid-structure solver based on the sharp-interface immersed boundary method is employed. The cylinder is kept in the uniform flow stream and is mounted elastically such that it is constrained to move in the transverse direction to the flow. The surface of the cylinder is heated at a prescribed temperature, and the thermal buoyancy is imposed in the transverse direction to the flow. Simulations are performed for the following parameters: Reynolds number Re = (50, 150), Prandtl number Pr = 7.1, mass ratio m = 2, reduced velocity UR = [4–15], and Richardson number Ri = [0–4]. We found that the thermal buoyancy could suppress or agitate the VIV. At lower Re (=50) and Ri = (1, 2), we observe the suppression in the VIV; however, there is no suppression for higher Re (=150) for these values of Ri. Galloping is observed for higher values of Ri = (3, 4) for Re = (50, 150). The galloping has been reported for rotationally asymmetric bluff bodies (e.g., D-section cylinder) in previous studies in isothermal flows. We show that a circular cylinder, a rotationally symmetric body, exhibits galloping due to the transversely acting thermal buoyancy at higher Ri.

Compositional Attention Networks with Two-Stream Fusion for Video Question Answering.

Given a video, Video Question Answering (VideoQA) aims at answering arbitrary free-form questions about the video content in natural language. A successful VideoQA framework usually has the following two key components: 1) a discriminative video encoder that learns the effective video representation to maintain as much information as possible about the video and 2) a question-guided decoder that learns to select the most related features to perform spatiotemporal reasoning, as well as outputs the correct answer. We propose compositional attention networks (CAN) with two-stream fusion for VideoQA tasks. For the encoder, we sample video snippets using a two-stream mechanism (i.e., a uniform sampling stream and an action pooling stream) and extract a sequence of visual features for each stream to represent the video semantics with implementation. For the decoder, we propose a compositional attention module to integrate the two-stream features with the attention mechanism. The compositional attention module is the core of CAN and can be seen as a modular combination of a unified attention block. With different fusion strategies, we devise five compositional attention module variants. We evaluate our approach on one long-term VideoQA dataset, ActivityNet-QA, and two short-term VideoQA datasets, MSRVTT-QA and MSVD-QA. Our CAN model achieves new state-of-the-art results on all the datasets.

Distributed Uniform Streaming Framework: An Elastic Fog Computing Platform for Event Stream Processing and Platform Transparency

The increase of Internet of Things devices and the rise of more computationally intense applications presents challenges for future Internet of Things architectures. We envision a future in which edge, fog, and cloud devices work together to execute future applications. Because the entire application cannot run on smaller edge or fog devices, we will need to split the application into smaller application components. These application components will send event messages to each other to create a single application from multiple application components. The execution location of the application components can be optimized to minimize the resource consumption. In this paper, we describe the Distributed Uniform Stream (DUST) framework that creates an abstraction between the application components and the middleware which is required to make the execution location transparent to the application component. We describe a real-world application that uses the DUST framework for platform transparency. Next to the DUST framework, we also describe the distributed DUST Coordinator, which will optimize the resource consumption by moving the application components to a different execution location. The coordinators will use an adapted version of the Contract Net Protocol to find local minima in resource consumption.